The present invention relates to a tank for a motorised compressor (moto-compressor), more particularly for an installation for isotopic separation by gaseous diffusion.
It is known that such installations in general have a cascade of units or separation stages, each constituted by a generally cylindrical column positioned vertically and supported by a horizontal supporting plate. From bottom to top each column has a separation chamber, a heat exchanger and a double flow axial motorised compressor. The gas to be treated arriving at high pressure from the motorised compressor of the upstream stage is separated in the separating chamber into a medium pressure flow and a low pressure flow on either side of porous barriers, the difference in these pressures being due to the pressure drop on passing through the same. The medium pressure flow is then taken up by a by-pass pipe and is returned to the upstream stage, whilst the low pressure flow is directed towards the motorised compressor located at the base of the column and in which it is mixed with the medium pressure flow from the downstream stage. The two flows are forced back under high pressure towards the following stage and so on throughout the entire cascade. In each stage the heat exchanger positioned between the separating chamber and the motorised compressor is traversed by the low pressure flow which enters the latter and by the high pressure flow at the outlet of said motorised compressor, so that the former recovers the calories acquired by the latter during its compression.
According to one construction of this type, the motorised compressor is advantageously suspended at the base of the column in each stage which permits an easy disassembly thereof. Moreover, the use of an axial motorised compressor makes it possible to ensure a direct intake of the low pressure flow at the outlet from the exchanger in the compressor rotor which reduces pressure drops and the danger of leaks. However, in this solution the intake of medium pressure flow to be recycled in the motorised compressor and which comes from the downstream stage makes it necessary to have a pipe connected laterally to the tank forming the lower part of the column, said pipe being positioned above the pipe via which is forced back the mixed flow at high pressure on leaving the motorised compressor. As a result the latter must have a relatively large size and the tank dimensions are considerably increased.
To obviate this disadvantage, it has already been proposed that the intake pipe for the medium pressure flow to be recycled be arranged in such a way that it traverses the diffuser provided inside the tank for collecting the high pressure flow when it leaves the rotor of the motorised compressor. However, in this case other problems occur, particularly due to the differential expansion rates between the members contained in the tank and in particular between the medium pressure flow supply pipe and the diffuser receiving the high pressure flow because said two flows are at different temperatures.